java - 如何使用 iText 生成目录 "TOC"？

Question

我创建了一个包含一些章节的文档。

如何为该文档生成 TOC？

它应该是这样的:

TOC:
Chapter 1                        3
Chapter 2                        4
Chapter 3                        6
Chapter 4                        9
Chapter 5                       10

Answer 1

这可以通过使用 PdfTemplate 来实现。 PdfTemplate 是一种您可以在之后填充的占位符。

根据 Bruno 的提示进行更新:

要在TOC一开始生成，需要为TOC中的所有页码放置一些Placeholders。您在 Map 中收集的那些 PdfTemplate。然后，当您将 Chapter 添加到文档时，您可以填充这些占位符。

这个例子展示了如何:

package com.example.main;

import java.io.FileOutputStream;
import java.util.HashMap;
import java.util.Map;

import com.itextpdf.text.Chapter;
import com.itextpdf.text.Chunk;
import com.itextpdf.text.Document;
import com.itextpdf.text.DocumentException;
import com.itextpdf.text.Font;
import com.itextpdf.text.FontFactory;
import com.itextpdf.text.PageSize;
import com.itextpdf.text.Paragraph;
import com.itextpdf.text.pdf.BaseFont;
import com.itextpdf.text.pdf.PdfContentByte;
import com.itextpdf.text.pdf.PdfPageEventHelper;
import com.itextpdf.text.pdf.PdfTemplate;
import com.itextpdf.text.pdf.PdfWriter;
import com.itextpdf.text.pdf.draw.VerticalPositionMark;

public class Main extends PdfPageEventHelper {
    private final Document document;
    private final PdfWriter writer;
    private final BaseFont baseFont = BaseFont.createFont();
    private final Font chapterFont = FontFactory.getFont(FontFactory.HELVETICA, 24, Font.NORMAL);

    // table to store placeholder for all chapters and sections
    private final Map<String, PdfTemplate> tocPlaceholder = new HashMap<String, PdfTemplate>();

    // store the chapters and sections with their title here.
    private final Map<String, Integer> pageByTitle = new HashMap<>();

    public static void main(final String[] args) throws Exception {
        final Main main = new Main();

        main.document.add(new Paragraph("This is an example to generate a TOC."));
        main.createTOC(10);
        main.createChapters(10);
        main.document.close();
    }

    public Main() throws Exception {
        this.document = new Document(PageSize.A6);
        this.writer = PdfWriter.getInstance(this.document, new FileOutputStream("test.pdf"));
        this.writer.setPageEvent(this);
        this.document.open();
    }

    @Override
    public void onChapter(final PdfWriter writer, final Document document, final float paragraphPosition, final Paragraph title) {
        this.pageByTitle.put(title.getContent(), writer.getPageNumber());
    }

    @Override
    public void onSection(final PdfWriter writer, final Document document, final float paragraphPosition, final int depth, final Paragraph title) {
        this.pageByTitle.put(title.getContent(), writer.getPageNumber());
    }

    private void createTOC(final int count) throws DocumentException {
        // add a small introduction chapter the shouldn't be counted.
        final Chapter intro = new Chapter(new Paragraph("This is TOC ", this.chapterFont), 0);
        intro.setNumberDepth(0);
        this.document.add(intro);

        for (int i = 1; i < count + 1; i++) {
            // Write "Chapter i"
            final String title = "Chapter " + i;
            final Chunk chunk = new Chunk(title).setLocalGoto(title);
            this.document.add(new Paragraph(chunk));

            // Add a placeholder for the page reference
            this.document.add(new VerticalPositionMark() {
                @Override
                public void draw(final PdfContentByte canvas, final float llx, final float lly, final float urx, final float ury, final float y) {
                    final PdfTemplate createTemplate = canvas.createTemplate(50, 50);
                    Main.this.tocPlaceholder.put(title, createTemplate);

                    canvas.addTemplate(createTemplate, urx - 50, y);
                }
            });
        }
    }

    private void createChapters(final int count) throws DocumentException {
        for (int i = 1; i < count + 1; i++) {
            // append the chapter
            final String title = "Chapter " + i;
            final Chunk chunk = new Chunk(title, this.chapterFont).setLocalDestination(title);
            final Chapter chapter = new Chapter(new Paragraph(chunk), i);
            chapter.setNumberDepth(0);

            chapter.addSection("Foobar1");
            chapter.addSection("Foobar2");
            this.document.add(chapter);

            // When we wrote the chapter, we now the pagenumber
            final PdfTemplate template = this.tocPlaceholder.get(title);
            template.beginText();
            template.setFontAndSize(this.baseFont, 12);
            template.setTextMatrix(50 - this.baseFont.getWidthPoint(String.valueOf(this.writer.getPageNumber()), 12), 0);
            template.showText(String.valueOf(this.writer.getPageNumber()));
            template.endText();

        }
    }
}

生成的 PDF 如下所示: TableOfContents.pdf